The accepted standard in neutron detection has been based on helium-3 (He3). One problem with conventional neutron detectors based on helium-3 is that helium-3 is a natural resource with a very limited supply. These types of detectors and all other known neutron detectors have a gamma rejection of approximately up to 4 gamma pulses in 10,000 pulses detected. Unfortunately, these levels of gamma rejection in conventional neutron detectors can result in too many false positive alarms, indicating that a neutron particle has been detected when in reality a gamma particle was detected. Gamma particles can occur from natural phenomena, such as from the sun, while neutron particles typically indicate a presence of radioactive and/or fissile material. Accurate detection of the occurrence of the neutron particles, without false detection of gamma particles as neutron particles, is critical for monitoring border activities such as during homeland defense and security.
The need for an efficient neutron detector, with little to no false positive alarms due to gamma cross-talk, is critical in many applications such as for homeland security, medical applications, and military applications. There is also a great need for neutron detectors that are not based on helium-3 due to the limited resources of helium.
There are technologies that enable neutron detection without the use of helium-3. For example, some technologies use lithium-6 dissolved uniformly into a plastic or glass scintillator. While these approaches have advantages, they are difficult to produce in volume with consistent performance characteristics and have difficulty based on light leaks into the detector area. These devices produce much less light per event and require much more gain in the photomultiplier tube (PMT). These types of devices also have increased gamma ray sensitivity and use analog techniques to separate gamma from neutron events which typically result in gamma pulse rejection rates of 4 in ten thousand, leaving an unsatisfactory rate of gamma false positives (gamma cross-talk).
There is also a need for a reliable and efficient production method to produce neutron detectors in volume.